Online Encyclopedia
Sweet potato
| Sweet Potato | ||||||||||||||
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| Ipomoea batatas Linnaeus, |
The sweet potato is a crop plant, Ipomoea batatas, whose large, starchy, sweet-tasting tuberous roots are an important vegetable. The young leaves and shoots are minor vegetables. Another name commonly applied to orange-fleshed varieties of sweet potatoes in the USA is "yam". Most botanists consider this an erroneous name since there are already other vegetables called yams (genus Dioscorea), which are not botanically related to the sweet potato. The sweet potato is also not particularly related to regular potato, which is sometimes called Irish potato to distinguish it. Those two plants are in different families.
The genus Ipomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. Some variants of Ipomoea batatas are grown as houseplants.
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Description
The edible root is long and tapered, with a smooth skin. Its flesh ranges from white to yellow, orange, or purple. All varieties are more-or-less sweet-flavored. The storage root is not actually a tuber even though it looks like one, since it develops from root tissue, rather than stem tissue as true tubers do. Some botanists describe it as a tuberous root.
Under optimal conditions of 85--90% relative humidity at 13--16°C, sweet potatoes can keep for six months. Colder temperatures injure the roots.
Sweet potatoes are rich in dietary fiber, vitamin C and vitamin B6. In some tropical areas they are a staple food crop. The storage roots, leaves and shoots are all edible. The storage roots are most frequently boiled, fried or baked. They can also be processed to make starch and a partial flour substitute. All parts of the plant are used for animal feed. Industrial uses include the production of starch and industrial alcohol.
Cultivation
The plant is an perennial vine that does not tolerate frost. It grows best at an average temperature of 24°C. Depending on the variety and conditions, tuberous roots mature in 2--9 months. With care, early-maturing varieties can be grown as an annual summer crop in temperate areas, such as the northern USA. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are mostly propagated by stem or root cuttings or by adventitious roots called slips that grow out from the tuberous roots during storage. True seeds are used for breeding only.
Production statistics
According to FAO, 98% of world sweet potato production occurred in developing coutries in 1994. China alone made up 84% of the harvest, producing about 105,000 tonnes on 65 km².
Though sweet potato production in the USA is minuscule compared to the world total, it is important regionally. The U.S. Southern states are a traditional sweet-potato-producing area. Marketers there use the term "yam sweet potato" to distinguish moist-fleshed, orange varieties of sweet potato from drier, white varieties. The true yam is nearly unknown in the USA except as an import sold in ethnic markets.
Origin
Sweet potatoes are believed to have originated in South America and spread throughout the tropical Americas into the Caribbean and across the South Pacific to Easter Island. Very likely the tuber drifted across the sea just as coconuts and some other plants still do today.
Because the general Polynesian word for the sweet potato is kumara, and the South American word is kumar, it was originally thought that this was evidence of cross-Pacific contact between South America and Polynesia. However, linguists have determined that kumara and kumar are totally unrelated and have nothing to do with each other. This therefore cannot be considered as evidence of pre-Magellan trans-Pacific crossing s.
Other meanings of the term sweet potato
Sweet potato is also a nickname for the ocarina, a wind instrument.